The semantic web provides a common framework that allows semantic data to be shared and reused across applications, enterprises, and community boundaries. The semantic web can be described as a web of data, such as dates, titles, part numbers, chemical properties, and any other conceivable semantic data that can be published and linked so that the data is available to anyone wanting to access it. The technical standards commonly used with the semantic web include: RDF (Resource Description Framework), which is a data modeling language for the semantic web used to store and represent semantic information; SPARQL (SPARQL Protocol and RDF Query Language), which is an RDF query language designed to query data across various systems; and OWL (Web Ontology Language), which is a schema language or knowledge representation language used to define concepts that can be reused.
Ontologies (also called vocabularies) are building blocks for inference techniques used on the semantic web. Ontologies are used to define concepts and relationships that describe and represent an area of concern that may be provided through the semantic web. Ontologies are used to classify terms which can be used in a particular application, characterize possible relationships, and define possible constraints on using the terms. In practice, ontologies can be very complex (e.g., with several thousands of terms) or very simple (e.g., describing just one or two concepts).